Used Bike Guide – Exhaust

Look for holes (from a crash or from advanced rust.) Sometimes you can hear exhaust leaks, usually as a sort of”chuffing” sound made as exhaust pulses escape through the rust hole.

Rust on the exhaust is usually on the surface only, and thus merely cosmetic, but advanced rust (older bikes?) may have caused holes in the exhaust pipes, requiring replacement. It is possible to patch holes in exhaust pipes, but it rarely looks good, and it also rarely makes sense — often the pipes rust in a number of places, not just one. It probably isn’t worth it to patch them all, but that’s up to you and your local exhaust shop.

Exhaust pipes are a common aftermarket accessory…. Loud pipes don’t “save lives” (a common motorcycle aphorism), they attract cops. But they also sound nice. : )

If the bike has more than one exhaust cannister, start the engine and, holding a piece of paper (not your hand) a few inches back from the exhaust tips, feel to see if the pressure coming from each cannister is roughly equal. It should be — if it isn’t, one of the cylinders probably isn’t firing. (You don’t want to use your hand for this because if the bike backfires, anything behind the exhaust pipes is going to get badly burned.)

This next step is optional and should only be performed if you have easy and unrestricted access to the exhaust pipes. If you want to try this, rehearse it with a “dry run” when the engine and the exhaust pipes are cold – having your arm halfway trapped in a confined space next to thousand-degree pipes is not a good situation to get into.

Be extremely careful with this step, and only do it if you’re confident that you can do this without burning yourself! Cover your fingers in a folded-up & thoroughly water-soaked paper towel, and very briefly touch each individual exhaust header pipe [1], about 7-9″ from where it comes out of the engine. (The header pipes will potentially be over a thousand degrees, so you don’t want to touch the paper towel to them for long at all! Try to do this shortly after the engine has been started.) Hissing indicates a hot pipe; a cold pipe (when others are hot) indicates a cylinder that isn’t firing. A variety of things could cause this — no spark, clogged carburators, vacuum leak, etc., so it’s hard to give you an idea of how much it would cost to repair. Probably between £5 and £200, once the specific problem is identified. If you’re hearing a hissing sound from where you touched the pipes, and you’re not using the wet paper towel trick (mentioned above), that’s your skin that’s hissing as it burns — you’re giving yourself third degree burns, and you should stop immediately.